US3520764A - Synthetic leather materials - Google Patents

Description

United States Patent 3,520,764 SYN THETHC LEATHER MATERIALS Richard C. Hoch, Quakertown, Pa., assignor to W. R.

Grace & Co., Cambridge, Mass, a corporation of Connecticut No Drawing. Continuation-impart of application Ser. No. 482,921, Aug. 26, 1965. This application Feb. 5, 1969, Ser. No. 796,888

Int. Cl. D06n 3/00; 1332b 29/02 U.S. Cl. 161-82 12 Claims ABSTRACT OF THE DISCLOSURE A cellulosic web which has been impregnated with a polymeric binder and a compound which can be a glycol, polyoxyethylene lanolin, silicone oil or an alkyl ester of a fatty acid, is compressively shrunk to produce a smoothersurfaced product improved with respect to the properties of flexibility and stiffness. The impregnated web may be secured to a dimentionally stabilizing fabric.

This application is a continuation-in-part of application Ser. No. 482,921 filed Aug. 26, 1965, and now abandoned.

This invention relates to a synthetic leather or coating base material characterized by leatherlike feel, resilience, and texture.

A number of substitutes for leather have come into general use. Such materials include plastic films, coated fabrics, and coated or uncoated papers and are usually stronger, more abrasion resistant, more waterproof, and generally more uniform in properties than leather. Synthetic leathers are utilized for shoe uppers, leather coats, gaskets, gloves, slippers, luggage, brief cases, camera cases, bags, and the like.

It has now been found that a novel synthetic leather structure characterized by improved internal bonding strength, resilience, reduced piping, and particularly improved flex life can be prepared which comprises an extensibilized, preferably biaxially extensibilized, nonwoven Web of cellulosic fibers which have been impregnated with a composition containing a polymeric binder material and a specified additive.

Extensibilizing or compressive shrinking of webs is known to the art. US. Pats. Nos. 2,624,245, 3,122,469, and 3,055,496 are directed to cellulosic webs which have been compressively shrunk and to apparatus for accomplishing the shrinkage. It has now been found that a superior product having a significantly improved flex life can be prepared by compressively shrinking a nonwoven cellulosic web which has been impregnated with a polymeric binder and a specified additive, described below. The compressive shrinking of the web is carried out after impregnation but while there is still moisture in the fiber, e.g., about 20 to 30%, or on the dried impregnated web. Preferably, the compressive shrinking is accomplished after the impregnation of the nonwoven web while the web still has moisture content of about 25%. However, improvement in the properties of the product, particularly with regard to flex life over comparable impregnated webs which have not been impregnated with a composition containing the additive of the invention or which have not been compressively shrunk are noted regardless of when the compressive shrinking is accomplished. The webs of the present invention are preferably shrunk 1 to 35% ice in one direction, and more preferably, 1 to in both he machineand cross-direction.

The term cellulosic web refers to a web made by conventional techniques, and particularly by wet-method paper-making techniques from conventional cellulosic pulps wherein there is some hydration bonding of the relatively short fibers in the web. The nonwoven webs are employed in the form they come off the web-making equipment, or alternatively they are pressed to increase the density. The weight of the nonwoven webs ranges from lbs/3000 sq. ft. to 200 lbs/3000 sq. ft., preferably lbs. to lbs. per 3000 sq. ft. If drying of the webs is desired, conventional methods are employed.

The additives employed in the present invention are glycols, polyoxyethylene lanolin, silicone oil, dioctyl phthalate and alkyl esters of fatty acids, e.g., butyl oleate. A particularly preferred class of additives are the glycols, especially polyglycols, e.g., ethylene glycol and polypropylene glycol. The additives are preferably employed at a level of about 5 to 30% by weight based on the weight of the fibers and more preferably 15 to 20%.

The additive of the invention is preferably introduced into the nonwoven web as a component of the impregnating composition. However, the additive may be applied, e.g. by spraying or dipping the Web into a bath of the additive before or after the impregnation step.

Polymeric binder materials known to the art are employed in the impregnating composition. Binders are polymeric elastomers having high adhesion to the fiber a minimum elongation of 400%, a minimum tensile strength of 50 p.s.i., and a maximum modulus of elasticity of 1000 p.s.i. Particularly preferred binders are carboxylic butadiene-containing polymers. In a preferred embodiment a small amount, e.g., 5% or less of a wet strength resin such as phenol formaldehyde or melamine formaldehyde, is also employed. The level of impregnation of the polymer on the fiber generally ranges between 50 and 150% by weight based on the weight of the fiber. Preferably, an impregnation level of about 100% is employed.

As example of suitable impregnating binders, mention may be made of natural and synthetic rubbers such as butadiene-styrene coploymers, butadiene-acrylonitrile copolymers, neoprene and the like. Other saturants are described in the following US. Pats. 2,410,078, 2,416,232, 2,438,195, 2,441,523, 2,692,253, 2,760,884, 2,799,596, 2,848,105, 2,848,344, 2,899,353, 2,905,584, and 2,837,109.

Impregnating compositions may also contain antioxidants, fillers, thickeners, curing agents, and the like. Impregating materials in the Web are employed in both cured and uncured state. Preferably, the polymeric materials are employed as latices or water dispersions. Solids solutions and melts may also be employed.

The compressive shrinking is accomplished by compacting and rearranging the fibers through compression of the web between two complementary surfaces. One of the surfaces at the time of contacting the web is an expanded elastic adherent surface and the other is a stable, nonadherent surface such as a steel bar or roll. After being gripped between the two surfaces, the elastic surface is caused to contract which results in shrinkage of the Web. This shrinkage is best carried out at a web temperature in the range of 210 to 300 F. and under sufiicient compression perpendicular to the surfaces of the web to prevent more than a 5% increase in the thickness of the impregnated Web.

The Webs are compressively shrunk in a single direction by passing through the compressive shrinking machine in one direction or the webs may be compressively shrunk in two directions, i.e., the machine-direction (MD) and in the direction perpendicular to the machine-direction or the cross-direction (CD). Shrinkage in two directions is 1 were then subjected to the same tests as the unlaminated webs. The results of these tests are set forth in Table 1.

EXAMPLE 2 An impregnated web was prepared and processed using accomplished by passing the web through the apparatus 5 Same p f as Example 1 except that 1 described in US. Pat. No. 2,625,254, in one direction, Welght Percent basls) of latex was replaced with turning the web 90 and again passing it through the app y y y laIlQhIL paratus Shrinkage in two directions may l b accom- Table 1 shows the results of physical tests carried out plished by a Single pass through h device d ib d i on the above materials. Flex life was determined on a US. Pat. No. 3,122,469 which compressively shrinks the dQVICe that bent the Sample 111 a angle 90 tlmes P webs in both the machine-direction and the cross-direction mlhuteat the same time. The disclosures of U .S. Pats. Nos. 2,624,- TABLE 1 245; 3,055,496} and 3,122,469 are incorporated herein to Em mp1 Example 2 the extent applicable.

After t Web has been imprtgnated and compressively $312332$33k1115;655:1111: exit 12 1 1% shrunk, it may be employed in that form as synthetic Gurleystitfness,mgms 1,004x1,045 1,04511095 leather. In a preferred embodiment, however, the material Mei hours (MD X CD) 108 X 47 289 X185 lammated to a fabnc preferably a woven.f.abnc to In Table 2 the results of physical tests carried out on vide a greater degree of dimensional stability. The imthe laminates are reported.

pregnant-compacted material is also preferably coated with a polymeric material to simulate the finish of leather. TABLE 2 As examples of a suitable coating, mention may be made Example 1 Example 2 of flexible materials such as a polyurethane, a plasticized Caliper (mils) 59 59 polyvinyl chloride or carboxylic butadiene-acrylonitrile Gurleystiflness, mgms a, 112x 2, 240 3,088 x 2, 054 copolymer whi h rovide a material with a scuff resistance Flex how (MD X CD) 43x43 262 X 538 greater than th hlgh water i iggg and 3 2 63 From the results of Table 1 it can be seen that the prod- VaPor Permeablhty of greater t an grams Per not which contained the polyoxyethylene lanolin additive Square meters. Per t 1 t t th 1 possessed a significantly greater flex life than the control,

The followmg non 1 fxamp es 1 us e e move 3 to 4 times as much, even at essentially the same stiffness Products of the presentmvemlon' level as the control, and therefore is more supple and EXAMPLE 1 more like natural leather. It should be further noted that (Control) the control has been subjected to a greater degree of shrinkage than the web of Example 2, but that the im- A cellulosic web having a ream weight of 139 pounds provement in flex life is still noted. was impregnated to a level of 100% by weight based on In Table 2 even greater improvement in flex life is the weight of the fiber of the following composition: reported; about 6 times in the MD flex life and about 11 times in the CD flex life. Percent IE 13110 td b d SBR latex '(76% butadiene, 23% styrene, 1% car- 40 n xfimp es o lmpregna e We 3 were prepare boxylic comonomer) 975 and laminated using the same procedure and materials as Phenol formaldehyde resin 20 in Example 1 except for the additive. The impregnating Sodium salt of ethylene diamine tetracetic acid 0.5 composltlon was as follows: Percent The levels of materials are on a weight-solids basis. The SBR latex 70% butadiene, 23% styrene, 1% impregnating composition had a total solids of 35%. After boxylic comonomer) 80.0 impregnation and squeezing out the excess saturant with Fib l b i 17 5 squeeze rolls, the web was dried at room temperature to Phenol formaldehyde resin 2.0 equilibrium moisture content at relative humidity. s di l of h l di i t t i id 5 The samples were then wet with water to a moisture con- Th f n tent of about 30% of the fiber and compressively shrunk 50 e Spec c a 1 we was as 0 wherein the temperature in the nip of the compacting ma- Example 3Control chine was 200 F. and a compression of 18% of belt Example 4Sorbitol thickness was employed. Compressive shrinking was car- Example 5Polyethylene glycol ried out in both the machine-direction of the paper as Example 6Polypropylene glycol well as the cross-direction. The webs were then dried to Example 7--Polypropylene glycol a moisture content of about 5% by weight based on the Example 8--Butyl oleate weight of the fiber and then cured 1 minute at 375 F. Example 9-Dioctyl phthalate Some of the samples were tested at this point for Gurley Example 10Silicone oil TABLE 3 Percent Delamination Flex life Percent shrinkage Gurley resistance (hours) Example N0. impregnation MD x CD Caliper (mils) Ream weight stiffness (oz./in. width) MD x CD 103 17 x 19 32. 0 104 1, 602 x 1,157 51 87 x 87 101 15 x 12 37. 5 1, x 079 37 15 x 351 101 13 x 14 30. 0 94. 5 889 x 711 48 400 x 400 00 10 x 10 20. o 100 800 x 711 57 500 x 496 100 11 x i2 29. 0 100 ass x 711 58 500 x 500 100 14 x 14 27. 0 100 979 x 712 34 136 x 351 100 12 x 12 28.0 100 712 x 712 44 15 x 351 94 15 x 16 32. 0 94 1,068 x 889 26 424 x 136 stiffness, flex life, and delamination resistance. Others were laminated to a slack mercerized fabric by means of a neoprene solvent adhesive. After the adhesive dried, two plies were pressed together to a compression of 5 mils at a temperature of 225 F. for three minutes. The laminates 75 The results of Table 3 show the significant improvement in flex life by the employment of the additives of the invention. Examples 5, 6 and 7 wherein the preferred additive of the invention was employed exhibited significant improvement in fiex life in both the MD and the 6 5. An impregnated fibrous material particularly suited for use as synthetic leather comprising a compressively shrunk, cellulosic, fibrous web impregnated between about 50 and 150% based on the weight of the fiber with an elastomeric binder material and between about 5 and CD direction as well as significantly decreased stiffness.

In order to evaluate the eifect of the compressive shrinking operation on the properties of the materials, physical testing was carried out on materials in all respects identical to the materials described in Examples 3 to except that they did not undergo compressive shrinking. 30% based on the weight of the fiber with a glycol.

TABLE4 Delamination Flex life Percent Ream weight, Gurley stittresistance (hams) Example No. impregnation Caliper, mils lbs. rwss,mgms. (o7../1n.w1dth) MDXCD 102 30 105 2, 667 x 1,869 44 87 x 160 101 32 103 3,293 x 2, 047 37 x 135 100 32 100 2, 848 x ,869 44 15 x 400 95 32 98 3,026 x ,869 44 136 x 15 100 32 101 3, 293 x ,314 40 15 x 15 9s 30 98 1,778 779 15 x 15 100 28 100 1,869 x ,315 39 87 x 15 93 93 2, 667 x ,503 37 207 x 87 The results of Table 4 show that both compressive 6. The product of claim 4 wherein said glycol is a shrinking and the additive of the invention provide 20 polyglycol.

greater improvements in flex life. In general there is less flexibility when the sample has not been shrunk, and in most cases the flex life results are poorer than the control (Example 4) which contained no additive.

Delamination resistance is the force, expressed in units of ounces per inch of width, required to continue the splitting of the specimen into approximately two equal plies. On two specimens 10 inches x 1 inch, two strips of rug binding tape 9 inches in length, are placed so that approximately 0.5 inch of paper extends beyond each end of the tape. The specimens are pressed for 30 seconds at 275 F. and 5 psi. with about 0.5 inch of tape extending beyond the edge of the press. The two free ends of the tape are pulled until the specimen starts to separate into two approximately equal plies. The two free ends of the tape are then placed in the jaws of an Instrom Tester, and the machine was run at 10 inches/ minute.

Gurley stiffness is a measure of the force required to bend a specimen through a certain angle. Stiffness was determined on a Gurley stiffness tester.

The addition of the additive of the invention to the web provides a web surface substantially devoid of fissures and smoother than has been attainable heretofore. There is also an improvement in the property of stiffness of the webs providing a more leatherlike feel to the product.

I claim:

1. An impregnated fibrous material particularly suited for use as synthetic leather comprising a compressively shrunk, cellulosic, fibrous web impregnated between about 50 and 150% based on the weight of the fiber with an elastomeric binder material and between about 5 and 30% based on the weight of the fiber of a compound selected from the group consisting of glycols, polyoxyethylene lanolin, silicone oil, dioctyl phthalate and alkyl esters of fatty acids.

2. The product as defined in claim 1 wherein said compound is present at a level of 15 to 20%.

3. The product of claim 1 wherein said elastomeric binder material additionally contains a minor amount of a wet strength resin.

4. The product as defined in claim 1 wherein said web is compressively shrunk 1 to in the machinedirection and 1 to 35% in the cross-direction.

7. An impregnated, fibrous material particularly suited for use as synthetic leather comprising a compressively shrunk, cellulosic, fibrous web impregnated between about 50 and based on the weight of the fiber with an elastomeric binder material and between about 5 and 30% based on the weight of the fiber of a compound selected from the group consisting of glycols, pOlyoxyethylene lanolin, silicone oil, dioctyl phthalate and alkyl esters of fatty acids, and, secured to said impregnated fibrous web, a dimensionally stabilizing fabric.

8. The product of claim 7 wherein said dimensionally stabilizing fabric is a woven fabric.

9. The product of claim 7 wherein the impregnated fibrous web is coated with a polymeric material.

10. The product of claim 7 wherein said compound is a polyglycol.

111. An impregnated fibrous material particularly suited for use as a synthetic leather comprising a compressively shrunk, cellulosic, fibrous web impregnated between about 50 and 150% based on the weight of the fiber with an elastomeric binder and between about 5 to 30%, based on the weight of the fiber, of a compound selected from the group consisting of glycols, polyoxyethylene lanolin, silicone oil, dioctyl phthalate and alkyl esters of fatty acids, said impregnated fibrous web being adhesively secured to a dimensionally stabilizing fabric and having a surface coating of a polymeric material.

12. The material of claim 11 wherein said dimensionally stabilizing fabric is a woven fabric and said polymeric material is selected from the group consisting of polyurethane, plasticized polyvinyl chloride and a carboxylic butadiene-aerylonitrile copolymer.

References Cited UNITED STATES PATENTS 3,245,863 4/1966 Sonnichsen et al. 16l-82 X 3,317,335 5/1967 Marrinan et al. l17140 X WILLIAM D. MARTIN, Primary Examiner M. R. LUSIGNAN, Assistant Examiner US. Cl. X.R.